Method for determining an orientation of an object

ABSTRACT

A method for determining an orientation of an object includes determining a plurality of boundary values defining a predetermined range of movement of the object; dividing the range into position segments using the plurality of boundary values; moving a movable portion of the object to a current position; determining a change in object position by comparing a prior object position to the current position; determining the number of position segments corresponding to the change of the object position; outputting a signal corresponding to the number of segments to a control device; determining a scaling value for any or all of the position segments corresponding to a desired position amplification or position attenuation scheme; and controlling movement of a selected image or device based on the amplification or attenuation scheme such that movement of the moveable portion of the object causes disporportional movement of the image or device.

This is a division of application Ser. No. 07/984,560, filed Dec. 2,1992.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile production by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

The invention relates generally to position and/or orientation sensingdevices and more particularly to devices for facilitating the trackingof a head or other movable object.

Various devices are known for measuring the orientation of the head(head tracking). Head tracking finds many useful applications. Forexample, the military uses head tracking to aim gun turrets and toprovide heads-up tactical information for the pilot of an aircraft. Theprivate sector uses head tracking as a third hand to allow a handicappedindividual to steer a motorized wheelchair, or to allow an individual tomanipulate a cursor on a computer screen.

Another application includes the use of head tracking to provide avirtual environment for the user--generally known as "virtual reality".Teachings of such application may be found in U.S. Pat. No. 4,984,179(Waldern); U.S. Pat. No. 4,884,219 (Waldern); and U.S. Pat. No.5,130,794 (Ritchey). "Virtual reality describes the host of applicationsthat involve the use of a virtual environment to allow human-machineinteraction at a more intuitive level than by typing commands on akeyboard or using a mouse-type device to communicate with a machine.Head tracking is necessary to generate a first-person virtualenvironment. Typically, the user wears video screens over both eyes anda host computer generates three-dimensional views that correspond to theposition of the user's head.

With many known systems, a fixed reference point is compared with theposition or orientation of the head by linking the head to the fixedreference point by way of mechanical linkage, optic linkage, ultrasoniclinkage, or magnetic linkage, and measuring the position or orientationof the head relative to that fixed reference point. Such systems aredescribed in U.S. Pat. Nos. 4,954,815; 4,565,999; 4,682,159; 5,142,506;and 4,688,037. However, a problem arises with such known head trackingdevices since the fixed reference point is off of the body and requiresthe use of an off-the-body transmitter and receiver configuration thatlimits the user to a confined space because of the limited range of thetransmitters. Known mechanical linkage systems also constrain the user.

The transmitter-receiver configurations typically have a freedom ofmovement advantage over the mechanical linkage systems but generallyrequire more time to process the received electromagnetic signals beforethe position/orientation information may be output from the device. Thistime is referred to as latency or lag time. The off-body mechanicallinkage provides almost instantaneous output, or negligible lag time,but severely limits the movement range of the user. Furthermore, suchsystems tend to be complex and subsequently costly to manufacture anduse.

Another device, such as that disclosed in U.S. Pat. No. 5,068,645,offers an advantage over the off-the-body link by using gravity as itsfixed reference point and therefore contains only a receiver mounted onthe headset. This device is relatively non-restrictive to the user sincegravity exists everywhere on the earth. However, such a device may notbe readily used in low gravity applications or non-gravity applicationssuch as in outer space. Secondly, this device may be prone to a pendulumeffect- The device measures the head position by comparing theorientation of the head to the surface level of a liquid in a sphericalcontainer. The liquid's surface stays level due to gravity while theuser's head tilts the spherical container. However, the liquid will notstay perfectly level because of inertia, but will rock back and forthwhen the user's head moves quickly. Such a pendulum effect may hinderthe performance of this device. Thirdly, such a device typically onlymeasures the head's angle along a vertical axis. It cannot measure thehead's lateral movement along a second axis. Consequently there exists aneed for a head tracking device which overcomes the disadvantages of theaforementioned prior art devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a relatively simpleand inexpensive head tracking device that has negligible lag timesimilar to conventional mechanical linkage devices while allowing morefreedom of movement than the transmitter-receiver pair devices and theconventional mechanical linkages.

It is a further object of the invention to provide a head trackingdevice that affords lateral as well as vertical tracking.

Yet another object of the invention is to provide a head tracking devicefor the control of cursor movement or virtual image movement thatgenerates an output to a host computer in the form of relativeincremental head movements

A further object of the invention is to provide a head tracking devicewhich outputs head position information to a host computer in the formof an absolute measurement.

It is yet a further object of the invention to provide a head trackingdevice which allows a user to interact with the head tracking control toinitialize a plurality of predetermined boundary ranges which may beused to scale position measurements to allow a larger or smallerdisplacement of cursor movement, or other object movement, connected tothe head tracking device.

The disclosed head tracking device tracks the orientation of at least aportion of an object, such as the head, with respect to a referencepoint on the object, such as the torso or upper body area of a user. Thepresent invention is a novel device used to determine the orientation ofthe head along one or two axes. The invention includes a headset worn bythe user containing an orientation sensor that determines the angulardisplacement of the head relative to the torso or shoulder blade of theuser through an electromechanical linkage.

In a preferred embodiment, the electromechanical linkage includes aflexible rod, such as a plastic whip and attachment device that may befastened to a user's torso area and extends to a T-joint that isfastened to a signal generating device, such as a shaft of apotentiometer (variable impedance device), a rotary optical encoder orother suitable signal generating device. The signal generating device isfastened to the headset. The flexible rod contains a clasping device onone end that attaches to the user's clothing or other surface coupled tothe user. Another end of the rod reciprocates freely through theT-joint. When the user's head rotates left, right, up or down, theplastic flexible rod moves and rotates the shaft of the variableresistor which corresponds to the rotation of the head.

The variable resistor may be interfaced to the digital domain throughthe use of an analog-to-digital converter. This quantized digital valueis then processed by a host computer to control the movement of a cursoror movement of a vertical image or other selected mechanism. Thecomputer compensates for any physical discrepancy that exists from userto user through a compensation method.

When one orientation sensor is used, lateral head tracking isaccomplished. In this configuration, it is necessary that the movementof the shaft of the variable resistor is minimized when the user's headrotates up or down. This is accomplished by the flexible rod since it isfree to move up and down in the T-joint.

When two orientation sensors are provided on each side of the user'shead, lateral and vertical orientation of the head can be simultaneouslymeasured. The computer reads the value of each variable resistor and candetermine the orientation of the user's head by comparing the twovalues.

In another embodiment, an additional signal generating device, such as aslide potentiometer or slotted flexible rod with an optical sensor fordetecting vertical movement, is added to the single orientation sensorto facilitate detection of movement along both the vertical and lateralaxes.

One compensation method is disclosed which requires user interaction toset boundary positions to define a user's selected range of movement.The computer configures the tracking system foreach user by executing asoftware calibration program before the user uses the head tracker in anapplication. The method includes the steps of measuring positionsignals, such as voltage drops across the variable resistor, when theuser's head is turned to a plurality of boundary or reference positions,then adjusting each value measured by applying a process that utilizesthe memorized parameters.

The latency, or lag time, between the digitizing of the variableresistor's value, applying the adjustment method and outputting a finalvalue is negligible since it is below the noticeable threshold value oflag time that may be approximately 50 msec.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a user wearing an orientation sensingdevice for tracking lateral head movement in accordance with theinvention;

FIG. 2 is a cutaway perspective view of an orientation sensor as shownin FIG. 1 in accordance with the invention;

FIG. 3 is a schematic diagram of the orientation sensor connected to acomputing device to emulate a mouse or interface with a video gamecontroller;

FIG. 4 is a schematic diagram of the orientation sensor connected toserial A/D chip to interface to a video game;

FIG. 5 is a flow chart generally illustrating the process of emulating amouse using the orientation tracking device in accordance with theinvention;

FIG. 6 is a perspective view of a user wearing the inventive trackingdevice and turning his head laterally in either direction to illustratethe flexing action and rotation of the connecting member of theorientation sensor in accordance with the invention;

FIG. 7 is a perspective view of a user wearing two orientation sensorsto facilitate lateral and vertical orientation tracking in accordancewith the invention;

FIG. 8 is a perspective view of a user wearing one orientation sensor ofFIG. 2 on the temple area and another orientation sensor of FIG. 2 onthe back of the head to facilitate lateral and vertical orientationtracking in accordance with the invention; and

FIG. 9 is an partial cross-sectional view of another embodiment of anorientation sensor to facilitate lateral and vertical orientationtracking in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a preferred embodiment of a head tracking device 10worn by a user 12 about the head 14. For purposes of discussion, sincethe head 14 generally moves with respect to the torso area 16, shoulderblade or upper body area, head movement from left to right or right toleft will be considered lateral movement along one axis whereas headmovement in a vertical, up and down direction will be considered aslongitudinal movement along a second axis.

The head tracking device 10 includes a housing 18 for attaching to themovable portion of the object, such as the head 14. The housing 18 maybe a headset which in the case of a virtual reality application may havea visor 20 containing a plurality of video display screens (not shown).

The head tracking device 10 further includes an orientation sensingmechanism 22 or position sensor, such as an electromechanical linkageconfiguration, connected to the housing 18 and having an attachmentportion 24 adapted for attachment to a reference portion of the object,such as the torso 16. In the case of a person, the torso may beconsidered a substantially non-movable portion with respect to the head.

The attachment portion 24 connects to connecting member 26, such as aT-joint sleeve, through a flexible rod 28. For purposes that will becomeapparent later, the flexible rod should be made from a material havingsufficient memory, such as thermoplastic, so that the rod returns to anoriginal shape after flexing. The connecting member 26 attaches to asignal generating device 30, such as a rotary potentiometer (variableresistor) or optical rotary encoder, and responds to movement offlexible rod 28 to actuate the signal generating device 30. As shown inFIG. 2, the connecting member 22 may be a hollow T-joint having achannel 32 through which the flexible rod 28 may reciprocally slide, anda base 34 for rotatably connecting to a shaft 36 on the signalgenerating device 30. The signal generating device 30 may be arotationally adjustable 1 K variable potentiometer having threeconnecting leads 38 as known in the art. It will be recognized that thesignal generating device 30 may be another type of variable impedancedevice or any other suitable signal generating device such as a variableintensity optic sensor or the like.

The direction of reciprocation of the flexible rod 26 is shown by arrow40 whereas the rotational movement to vary the resistance of thepotentiometer is shown by arrow 42. The cross-sectional shape of theflexible rod 28 and the inside cross-sectional shape of the channel 32are formed to facilitate sliding of the rod 28 through the channel 32during longitudinal movement of the user's head while providing suitableclearance to facilitate rotation of the potentiometer shaft 36 duringlateral movement.

The flexible rod 28 may include an adjustable stop member 44 adapted forslidable adjustment along the length of the flexible rod 28. The stopmember 44 may be coupled distal the attachment portion 24 to prevent theflexible rod 28 from sliding entirely through the connecting member 26when the user puts the headset on or removes the headset.

The signal generating device 30 connects to a microcomputer 46 whichcontains an 8 bit analog-to-digital (A/D) converting circuit to convertthe analog signal to a digital signal as known in the art. Themicrocomputer may be a Motorola 68HC11 microcomputer which has on-boardROM and RAM so that the microcomputer 46 may be suitably programmed. Themicrocomputer 46 may be programmed to communicate via a standardprotocol to a host computer 48 to emulate a mouse. In the case of avirtual reality system, the host computer 48 may generate the imageinformation to be communicated to the display screens on the visor 20 inresponse to head orientation information as provided by themicrocomputer 46. Where the head tracking device is employed tofacilitate cursor movement on a display screen, the host computer 48 maybe a personal computer or other device utilizing a video display screen.

The attachment portion 24 includes a suitable clasping device orattachment device adapted to attach to a relatively non-movable portionof the object. For example, the attachment device 24 may be analligator-type clip 24a, a VELCRO™ attachment pad (not shown), or aninverted "U" member 24b adapted to rest on the shoulder (shown in FIG. 7) which may couple to the clothing, outer wear, or body of a user.

The flexible rod 28 should be of a flexible nature to allow relativelyfree movement of a user's head. For example, an unsuitably rigid rod mayrestrict the lateral movement of the user.

In operation, the user may rotate the head laterally along one axiswhich will, in turn, cause the flexible rod 28 to push against theconnecting member 26, thereby causing the connecting member 26 to rotateas indicated by arrow 42. During such lateral movement, the flexible rod28 is also allowed to reciprocate through the channel 32 of theconnecting member 26 to facilitate freer movement of the user's head.However, vertical movement of the head will also cause the connectingmember 26 to be slightly rotated by the flexible rod 28. Consequently,only a single orientation sensor 22 (as shown in FIG. 1) may be neededfor head tracking along a single lateral axis.

FIG. 3 schematically illustrates a head-tracking control circuit 50which includes the microcomputer 46 connected to the signal generatingdevice 30 to determine the orientation of the head. The microcomputer 46also communicates with the host computer 48 via EIA RS-232A protocolusing a plurality of bidirectional ports (PD0 and PD1). The controlcircuit 50 includes a clock 52 for supplying timing pulses to themicrocomputer 46 and a transistor 56 such as an N-Channel FET, for useto receive information during RS-232 communication.

A plurality of visual indicators (LED's) D0, D1 and D2 connect to themicrocomputer 46 and are activated to indicate the reference or boundarypositions as selected by the user, such as the leftmost position of theuser's head, the right-most position of the user's head, and the centerposition of the user's head. The LED's D0, D1 and D2 may be mounted onthe visor 20 so that the user can tell when he has reached the lateralposition limits of the head tracking system or may be mounted externallyto the headset. Such visual feedback to allow a user to set boundarypositions may also be carried out on screen (display devices on thevisor in the case of a virtual reality application) via computer controlor may not be necessary where such boundary positions are predetermined.

A plurality of resistors 58 and 60 serve to terminate pins on themicrocomputer 46 as known in the art. A reset integrated circuit 66,such as a Motorola MC34164, serves to provide a reset condition duringpower-up but may not be necessary with another suitable type ofcomputing device.

As shown, a first connecting lead of the potentiometer (variableresistor) may be connected to a power supply, a second connecting leadmay be connected to a ground return line, and a signal connecting leadmay be connected to an A/D input port on the microcomputer 46. Where twoorientation sensors are used (best seen in FIG. 7), a second sensor 102may be connected to the microcomputer by connecting the first connectinglead of each potentiometer in common on the headsets and connecting thesecond connecting leads in common so that only the signal connectinglead from the second sensor 102 needs to be connected to the externallymounted microcomputer 46.

The tracking device may be used with a number of different methods fordetermining the orientation of the user's head to control a cursor orotherwise move a virtual image or machine such as a medical operatinginstrument. One method outputs the relative change of the user's headorientation to a control device such as the host computer while anothermethod outputs an absolute value corresponding to the orientation of theuser's head.

FIG. 4 schematically illustrates the use of the tracking device 10 asinterfaced with a video game. The signal generating device 30 connectsto an A/D integrated circuit 70, such as an LTC1096 which converts theanalog voltage generated by the signal generating device 30 into adigital position value. The position value is communicated to a gameconnector 72 which interfaces with a game controller (not shown). Thegame controller carries out the necessary computing so that themicrocomputer 46 is not needed. A transistor 74 connected to the latchoutput from the controller serves as a signal inverter which is neededin this case to interface with a NINTENDO™ game unit (not shown). TheA/D converter 70 converts the position signal to a digital signal andtransmits the digital signal to the game controller for its use indetermining the movement of the cursor or image.

FIG. 5 is a flow diagram generally indicating a method of determiningthe relative change of head orientation that may be used by the computer46, or host computer, to determine the lateral orientation of the headand control the position of a cursor on a screen. The processcompensates for physical variances between user's head movement ranges,e.g. users having different maximum and minimum angular displacements inthe lateral direction.

In block 80 the method starts by initializing the microcomputer 46 orotherwise setting the appropriate inputs to a level to begin headtracking. After the system has been initialized, an alignment processbegins as shown in step 82. The alignment process starts with the userdefining a range of lateral head movement. The microcomputer 46activates an indicating device such as DO to inform the user to move hishead to a left boundary position. The user moves the head to a desirableleft boundary position and activates the pushbutton switch 68. Themicrocontroller 46 reads the voltage value from the signaling device 30to determine a left boundary value. Next, the microcomputer 46 activatesD1 to inform the user to move his head right, to a selected rightboundary position. The user then activates the pushbutton switch 68 toset the right boundary value.

In a like manner, a center LED, D2 is lit by the microcomputer 46 toinform the user to move his head to a center position and activate thepushbutton switch 68 to set the center boundary value. With reference tomoving a cursor, the microcomputer through communication with the hostcomputer, determines the number of position segments or "mickeys" (aterm used when referring to mouse usage) between the left boundary andthe center boundary. This corresponds to the number of cursor positionsfrom a half-screen to the left of the screen. In a like manner, thecomputer also divides the range from the right to the center boundaryposition to determine a number of position segments between the centerposition and the right position. This corresponds to the number ofcursor movements per half-screen from the center of the screen to theright of the screen.

In step 84, the user moves his head to a current position. Next, themicrocomputer 46 determines whether the voltage reading corresponding tothe current position is left of center as shown in step 86. If thecurrent value is left of center, the microcomputer 46 determines whetherthe prior position was left or equal to center as shown in step 88. Ifthe prior position signal was left or equal to center, the currentposition value is subtracted from the prior position value to give arelative change in position value as indicated in step 90. This changein position value is then stored in a register after which time a readstatus signal from the game controller is acquired as shown in step 92.The change in position value as determined in step 90 is then used instep 94 to generate a packet of information understood by the controldevice or host computer. The change in position value is thentransmitted in the form of a packet to the host computer as shown instep 96. If the user no longer wishes to use the head tracking device,the user may then indicate an end session as shown in step 98 whereafterthe microcomputer 46 will stop and the process ends as shown in step100. However, the process may continue continuously to give a currentposition reading of the user. Consequently, the microcomputer 46 willobtain a current signal in step 84 and repeat the orientationdetermination process.

Referring back to step 88, if the current signal value is left ofcenter, but the prior signal was not left or equal to center, then thecomputer computes a change in position value equal to the center valueminus the prior value plus the current position minus the centerposition as shown in step 102. This information is then sent back to thehost in a packet of information as previously described. Where thecurrent position is not left of center, the computer determines if theprior signal is to the right or equal to center as shown in step 104.Where the prior signal is to the right or equal to center, the change inposition value as shown in step 106 is determined by subtracting thecurrent value minus the prior value. However, where the prior value fromstep 104 is not to the right or equal to the center value, the change inposition value is determined by subtracting the prior value from thecenter value and adding the result to the subtraction of the currentvalue minus the center value as shown in step 108. Consequently, theaforedescribed method generates a relative change in relative positionsignal instead of an absolute position indication signal.

To accommodate different applications, the change in position valuedetermined by the method shown in Fig- 5 may be scaled by a suitablescaling value to facilitate disproportional movement between a user'shead and the controlled unit such as the cursor, image, or a machine. Auser may wish to amplify or attenuate the position moved by the userbased on a desired amplification or attenuation scheme. For example,where the user desires a large change in head position to result insmall change in cursor movement, the change in position value may bescaled down and consequently attenuated so that the control device orvideo display device will not move the cursor in a proportional manner.Conversely, where the user desires a small movement of the head toresult in a large movement of the cursor or virtual image, the resultingvalue from the method in FIG. 5 may be amplified before being sent tothe control device to transform the small movement in the head to alarge movement of the cursor.

It will also be recognized by those skilled in the art that the use ofdetermining a center position may be unnecessary where a less accurateposition value would be suitable. Conversely, it will also be recognizedthat an increased number of predetermined boundary values may also beused to get a more accurate position determination. For example, insteadof using three boundary values corresponding to the left, center andright positions, a system may use four or more predetermined boundarypositions to get a more accurate reading of the lateral displacementthroughout the complete displacement range.

Another orientation detecting method which may be incorporated with theorientation sensor 22, may be referred to as an absolute positionindication method. In such a method, the predetermined range defined bythe position boundary parameters may be represented as a digital numberfrom 0 to 255 such that each incremental movement corresponds to a 1/256of the range. Hence a voltage reading corresponding to the currentposition will be converted be the A/D connecting circuit and used as theabsolute position value to indicate the current position of the head.Therefore, the microcomputer 46 need not go through the subtractionprocess of FIG. 5 to determine a change in position value which is sentto the host computer. Such a method may be suitable for controlling acursor in a game.

FIG. 7 illustrates a head-tracking device 100 which incorporates twoposition sensors 22 and 102 to provide both lateral and vertical headtracking- The second position sensor 102 is substantially identical tothat of position sensor 22 shown in FIG. 2. The two orientation sensors22 and 102 are attached to the housing 18 on either side of the user'shead approximate the temple area. It has been found that the sensors 22and 102 should be as close to the center line of the head as possible toobtain a more linear output from the sensors. However, practicalconsiderations such as comfort of the user should also be taken intoaccount.

The second orientation sensor 102 includes a signal generating device104 substantially identical to that of the orientation sensor 22. Bothsignal generating devices 30 and 104 are connected to the microcomputer46 as shown in FIG. 3 to provide head orientation signals to themicrocomputer 46.

In operation, the microcomputer 46 receives input signals from each ofthe signal generating devices 22 and 102. It has been found that each ofthe sensors may be actuated during movement. Consequently, not all headpositions generate unique position values. However, it has also beenfound that a small range of head movement may generate correspondingvalues that are unique for each position. Therefore, a one to onecorrespondence between the range of head movement and the range ofcursor movement may be facilitated through scaling as previouslydescribed. For example, the microcomputer 46 may scale the small rangeof unique values so that the small range of movement corresponds withcomplete coverage of the entire area of the display screen. Thus, asmall movement of the head may be transformed into a large movement ofthe cursor.

FIG. 8 shows a different location for the two orientation sensors 22 and102 wherein one orientation sensor 102 is positioned in the back of thehead along the center line of the head and the other sensor 22 remainsproximate the temple area. The placement of the sensor 102 in the backof the head along the center line of rotation affords more mutuallyexclusive position values for a wider range of head movement. When theuser moves the head in the lateral direction, both sensors 22 and 102are actuated. When the user moves the head in the vertical direction,the flexible rod 28a in the sensor 102 slides through the "T"-joint anddoes not significantly actuate the signalling device 104. As a result,more unique position values may be obtained with this configuration. Asshown, the flexible rod 28a may include a plurality of angles 106 and108 to allow the user to attach the flexible rod to the torso area ofthe user.

FIG. 9 depicts a portion of a single orientation sensor 150 formeasuring both lateral and vertical movement. The sensor 150 includes anadditional signal generating device 152 for detecting reciprocatingmovement of the flexible rod 28b during head movement. The flexible rod28b has a plurality of apertures 154 extending a suitable length alongthe rod. The signal generating device 152 may be an optical reflectancesensor 156 coupled to the microcomputer 46 and positioned in theconnecting member 26a adjacent the channel 32 to direct a beam of lightonto the flexible rod 28b. The apertures 154 serve to change the amountof optical energy reflected by the rod 28b and received by thereflectance sensor as the rod 28b reciprocates through the channel 32.Such reciprocating movement tends to be greatest when the user moves thehead along the vertical axis. Hence, vertical movement may be readilydistinguished from lateral movement. The size of the apertures 154 maygradually increase or decrease along the rod so that the direction (upor down) of the user may be readily ascertained.

Other types of signal generating devices may also be used to detectreciprocating movement of the flexible rod. For example, the pluralityof apertures may be eliminated by using a linear or slidingpotentiometer that may be coupled to the rod so that reciprocatingmovement of the rod actuates the potentiometer. The output from thepotentiometer may be coupled to another of the A/D inputs of themicrocomputer 46.

In general, it will be recognized that the attachment portion 24 of theorientation sensors may be attached to a relatively non-movable portionof the person which may be in an area other than the torso or upperbody. For example, a user may attach the attachment portion 24 to ashoulder blade area or side of the arm where the side of the arm doesnot move with respect to the head. In addition, it will be recognizedthat the terminology used herein of "attaching to a non-movable portion"of the user includes attachment to clothing or outer covering or othersurface which remains substantially fixed relative to the movement ofthe user's head. Therefore, a shoulder harness may also serve as asuitable attachment portion as shown in FIG. 7 for the orientationsensor 102.

Also, it will be recognized that yet another method for determining theboundary or range values of the total lateral movement of a user may bebased on a priori knowledge of a statistically determined angledisplacement range. For example, it may be determined that a typicaluser has a total angular displacement of 120°, as a result, a user mayforego the range setting process of activating the push button since thecomputer knows the range. Therefore, the computer may assume that theboundary values lie 120° apart where the center value lies at the 60°value.

The Appendix is a code listing of a program for use by the microcomputer46 of FIG. 3 to determine lateral head orientation in accordance withthe method described with reference to FIG. 5. The head orientation datais transmitted over the RS-232 interface in a format which emulates aMicrosoft™ mouse for an IBM PC™ compatible computer. This listingcontains material which is subject to copyright protection.

Specific embodiments of novel methods and apparatus for head trackinghas been described for the purposes of illustrating the manner in whichthe invention may be used and made. It should be understood that theimplementation of other variations and modifications of the invention inits various aspects will be apparent to those skilled in the art, andthat the invention is not limited by the specific embodiments described.It is therefore contemplated to cover by the present invention any andall modifications, variations, or equivalents that fall within the truespirit and scope of the basic underlying principles disclosed andclaimed herein.

What is claimed is:
 1. A method for determining the orientation of anobject comprising the steps of:determining a plurality of boundaryvalues defining a predetermined range of movement of the object;dividing the range into position segments using said plurality ofboundary values; moving a movable portion of the object to a currentposition; determining a change in object position by comparing a priorobject position to said current position; determining the number ofposition segments corresponding to the change of the object position;outputting a signal corresponding to said number of segments to acontrol device; determining a scaling value for any or all of saidposition segments corresponding to a desired position amplification orposition attenuation scheme; and controlling movement of a selectedimage or device based on said amplification or attenuation scheme suchthat movement of the moveable portion of the object causesdisporportional movement of said image or device.
 2. The method of claim1 wherein determining a plurality of boundary values comprises the stepsof:moving the movable portion of the object to a first boundaryposition; activating acquisition means to record said first boundaryposition; moving said movable portion to a second boundary position; andactivating acquisition means to record said second boundary position. 3.The method of claim 2 further comprising the step of activatingindication means to confirm recording of said first and second boundaryposition.
 4. The method of claim 2 wherein determining a plurality ofboundary values further comprises the steps of:moving the moveableportion of the object to a third boundary position located between saidfirst boundary position and said second boundary position; activatingacquisition means to record said third boundary position.
 5. The methodof claim 4 further comprising the steps of:determining the number ofposition segments between the first boundary position and the thirdboundary position; and determining the number of position segmentsbetween the second boundary position and the third boundary position. 6.The method of claim 5 further comprising the steps of:determining thecurrent position of the movable portion of the object relative to saidthird boundary position; and determining the prior position of themovable portion of the object relative to said third boundary position.7. The method of claim 4 further comprising the step of activatingindication means to confirm recording of said third boundary position.8. A method for determining the orientation of an object comprising thesteps of:determining a plurality of boundary values defining apredetermined range of movement of a moveable portion of a human bodyrelative to a human torso; dividing the range of movement of themoveable portion of the human body into position segments using saidplurality of boundary values; moving the moveable portion of the body toa current position; determining a change in the moveable portionposition by comparing a prior moveable portion position to said currentposition; determining the number of position segments corresponding tothe change of the moveable portion position; outputting a signalcorresponding to said number of segments to a control device;determining a scaling value for any or all of said position segmentscorresponding to a desired moveable portion position amplification ormoveable portion position attenuation scheme; and controlling movementof a selected image or device based on said amplification or attenuationscheme such that movement of the moveable portion of the body causesdisproportional movement of said image or device.
 9. The method of claim8 wherein determining a plurality of boundary values comprises the stepsof:moving the moveable portion of the body to a first boundary position;activating acquisition means to record said first boundary position;moving the moveable portion of the body to a second boundary position;and activating acquisition means to record said second boundaryposition.
 10. The method of claim 9 further comprising the step ofactivating indication means to confirm recording of said first andsecond boundary position.
 11. The method of claim 9 wherein determininga plurality of boundary values further comprises the steps of:moving themoveable portion of the body to a third boundary position locatedbetween said first boundary position and said second boundary position;activating acquisition means to record said third boundary position. 12.The method of claim 11 further comprising the steps of:determining thenumber of position segments between the first boundary position and thethird boundary position; and determining the number of position segmentsbetween the second boundary position and the third boundary position.13. The method of claim 12 further comprising the steps of:determiningthe current position of the movable portion of the body relative to saidthird boundary position; and determining the prior position of themovable portion of the body relative to said third boundary position.14. The method of claim 11 further comprising the step of activatingindication means to confirm recording of said third boundary position.